1. Field of the Invention
The present invention relates to method of producing a heat-sensitive recording material which is superior in stability of the base surface of a recording material and stability of an image recorded thereon.
2. Related Art
Recently the use of heat-sensitive recording materials which can record images by using heat energy has been growing in various fields such as facsimile, printers, recorders, typewriters, label printers, automatic vending machines for tickets, etc.
Such heat-sensitive recording materials which comprise electron-donating colorless dye precursors and electron-accepting color developers, have various superior properties including good appearance, good touch feel, high color density and various hues, but they suffer from the problems that if a colored portion (recorded image portion) contacts with plastics such as vinyl chloride, the portion disappears due to plasticizers or additives contained in the plastics, or if the portion contacts with chemicals contained in foods or cosmetics, it easily disappears or it is readily discolored upon exposure to the sun for a few hours, namely they have a defect of poor stability of recorded images.
As heat-sensitive recording materials which can give recorded images having good stability by the reaction of two components upon heating, Japanese Patent Kokai Nos. 58-38733, 58-54085, 58-104959, etc. disclose heat-sensitive recording materials prepared by using an isocyanate compound and an imino-compound as the two components.
These heat-sensitive recording materials having a heat-sensitive layer which is formed of an isocyanate compound and an imino-compound is superior in stability of the recorded image but they have defects in basic stabilities such as yellowing and fogging of non-recorded portions of the base.